The occurrences of diffuse scattering in the neutron diffraction patterns of the deuterides of Laves phase have frequently been reported, but have not been specifically studied. As the diffuse scattering indicates the formation of short range ordering of D and/or alloy atoms in the phase, we have particularly studied the possible short range ordering of interstitial D atoms in the deuteride of a null matrix Laves phase alloy Ti_0.68Zr_0.32MnCr by neutron and XRD techniques. The neutron diffraction pattern of the deuteride Ti_0.68Zr_0.32MnCrD_3.0 has shown not only the Bragg peaks, but also strong diffuse scattering, whereas the corresponding XRD pattern has only shown the Bragg peaks. These phenomena confirm the formation of short range ordering of interstitial D in the deuteride. The D occupancy and short range ordering of the deuteride were analyzed by the Rietveld refinement and Fourier transformation. The analyses suggest that a fraction of D atoms in the deuteride is randomly and unsaturatedly distributed in certain interstices, and forms a long range ordered structure in the crystal lattice. These interstitial atoms are in four types of the A₂B₂ tetrahedral sites, where the occupancies of the D atoms in the 6h₁ and 12k crystallographic sites are higher than those in the 6h₂ and 24l sites. However, other D atoms in the deuteride have stayed away from the centres of the interstitial sites to different extents, and formed the short range ordered structure. These D atoms keep an average interdistance of 0.243 nm for the nearest neighbours, larger than that of about 0.2 nm for the long range ordered D atoms. The short and long range ordered D atoms together form a cluster network surround the Ti/Zr atoms along the c--axis of the lattice. The phenomenon is likely to be caused by the accumulation of great amount of D atoms in the interstices of the alloy.

Cavitation erosion of materials is mainly caused by the impact of strong pressure pulses and high speed micro--jets, which is formed at the end of bubble collapse. Its mechanisms have been intensively studied based on cavitation tests of heterogeneous materials. Generally speaking, the metallic phase, which is softer and has lower yield limit than the other in a material, is damaged first. However, a metallic phase may perform distinctively in different materials. Satisfactory explanation of this phenomenon is far from being achieved and further studies are necessary. 
        The present work is devoted to the mechanical effect of the impact of the cavitation erosion on duplex steels. Vibration cavitation tests were conducted to mild, medium and high carbon steels which are composed of ferrite and cementite. Mass losses of materials during tests were recorded. Investigations were made on the variation of the microstructure and morphology of specimen surfaces by scanning electronic microscope (SEM) and surface profilometer (SP), as well as the peak strength of binding energy of elements by X--ray photo electron spectroscopy (XPS). It was found that the cavitation damage of all the materials tested is characterized by the serious deformation and fracture of the ferrite phase in them. But the appearance of cavitation surfaces differs from each other because the volume (or mass) fraction and distribution of ferrite are different. Mild carbon steel with dominating integral phase of ferrite deforms uniformly. Medium (hypoeutectoid) steel contains approximately the same fraction of reticulated ferrite as that of pearlite (composed of alternating lamellae of ferrite and cementite). Its deformation mainly occurring in ferrite phase makes the reticulated ferrite bulged up and spalled off the surface gradually. High carbon steel mainly composed of pearlite is damaged because the lamellar ferrite is expelled out and splitting occurrs at the phase boundaries between ferrite and cementite. Analysis with the application of stress wave theory shows that the particular patters of damage of these materials are contributed to the yield of lower strength phase caused by compression stress waves produced by the impact of micro--jets.

The principle purpose of surface modification by laser rapid melting solidification is to improve the surface properties of materals through the change of their surface microstructures. The γ/γ'–αMo directional eutectoid alloy consisting of a chemical composition (atomic fraction) of 15.41%Al, 2.56%V, 3.25%Cr, 8.41%Mo and balance Ni was chosen in the present study. The master alloy was melted in a vacuum induction furnace, and then the directional eutectoid specimens were prepared in a vacuum solidified furnace. Two ways, i.e. pulse and scan, were used for the surface laser  treatment. A finer directional eutectoid structure grows again in the melting zone when the laser pulse is parallel to the eutectoid growth direction. However, when the laser pulse is perpendicular to the eutectoid growth direction, the microstructures of melting zone are composed of much denser cell–like crystalline and dendrites. The dendritic arm in dendrite structure after laser melting consists of the γ–solid solution and the fine γ'–participites, and the microstructures in the interdendrites are composed of the γ–solid solution containing γ' and the metastable phase precipitates which are enriched by Mo. These metastable phases are the ordered [αMo_(ordered)], Ni₃Mo and ordered [Ni₃Mo_(ordered)].

Pitting corrosion of stainless steels is a very complex process in the chloride–containing media with sulfate–reducing bacteria (SRB). Sulfate reduction by SRB results in the production of sulfur–containing species, which can significantly change the media state and ultimately affect both the pit–initiation (breakdown of passive film) and the pit–growth. In the present study, the effect of SRB on the pitting corrosion behavior of 18–8 stainless steel (18–8SS) in seawater was investigated by atomic force microscopy (AFM) and electrochemical methods. As the results show, 18–8SS can be quickly activated in the media with SRB, indicating that bacterial activities can accelerate greatly the process of breakdown of passive film; Measurements with AFM probe demonstrate that the rate of micropit growth of 18–8SS in the media with SRB is conspicuously higher than that in the sterilized media. As for the pitting corrosion mechanism, bacterial metabolites make the pit potential (Epit) and the repassivation potential (Erep) both decrease distinctly; However, Epit of 18–8SS is still more positive than the redox potential (Eh) of the media state, Erep of 18–8SS more positive than the reversible hydrogen electrode potential, and thus it is proposed that the localized free oxygen resulting from sulfidation of passive film in the media with SRB is the main factor which causes the breakdown of passive film; Subsequently, sulfur element or polysulfide in the media with SRB is the main factor which sustains the pit–growth, and the current density for cathodic reduction of sulfur element or polysulfide can reach to a very high level (>10 μA/cm²).

Zirconium alloys are used extensively in nuclear reactor cores. During their service a part of hydrogen produced through the corrosion reaction of Zr with hot coolant is absorbed by materials. Hydride induced embrittlement significantly influences the in–service performance of the Zr–alloy components. Delayed hydride cracking (DHC) is a localized form of hydride embrittlement, consequently, hydrogen atoms in the solid solution will diffuse into this region ahead of the crack tip subjected to a triaxial state of stress, which may lower the chemical potential of the region. Once the hydrogen concentration in this region reaches the terminal solid solubility (TSS), hydrides will start to form and grow. When the hydrides at the crack tip reach a critical size, the main crack will propagate through this hydrided region. The crack front finally is arrested at the end of the hydrided region by the ductile zirconium matrix, and the whole process repeats itself.
        Most of the investigations on DHC in zirconium alloys are focused on Zr–Nb alloys. Few literatures were found on the subject of DHC in Zr–Sn alloys. The purpose of the present study was to investigate critical temperature for initiating and arresting delayed hydride cracking in Zr–Sn–Nb alloy.
        A critical temperature for DHC study was carried out to determine the critical temperature for initiating and arresting in N18 zirconium alloy (Zr–Sn–Nb alloy). For a given hydrogen concentration of a specimen, the two critical temperatures were observed—a DHC initiation temperature, T_c, at which DHC would initiate when approaching the test temperature from above the terminal solid solubility (Cd) temperature in hydride dissolution and a DHC arrest temperature, Th, obtained by heating the same specimen from T_c after DHC had started. T_c slightly below Th. Both T_c and T_h fall below the dissolution solvus temperature and above the precipitation solvus temperature. A theoretical analysis was carried out to quantitatively determine the hydrogen concentration limit and these critical temperatures using the method of Dutton and Plus, a key assumption in the method is that, while the local crack tip stress concentration causes a local enhancement of the hydrogen concentration in solution, the hydride precipitation solvus is unaffected by stress. Good agreements are obtained between measured and predicted values of critical temperatures, which support the Dutton--Plus theory.

As high–temperature structural materials, Ni₃Al possesses excellent comprehensive properties, such as good strength at high temperature, low density, excellent ductility, superior oxidation resistance and so on. A high performance Ni₃Al–based alloys IC6 has been developed by authors and successfully applied for aero–engine vanes. It has been found that the high temperature mechanical properties of the single crystal IC6 alloy are superior to both equiaxial crystal and directional columnar IC6 alloys. A lot of research work for IC6 alloys has been carried out on the equiaxial crystal and directional columnar IC6 alloys during the last two decades. In order to further improve the mechanical properties and meet the requirement of turbine blade materials, the single crystal Ni₃Al–based alloy IC6SX has been developed and the research work on single crystal processing has been carried out recently. In the present investigation, the influence of withdrawal rate on the microstructure and stress rupture properties of a Ni3Al–based single crystal superalloy IC6SX were studied. The single crystal specimens were prepared by screw selection crystal method. The microstructure analysis by SEM and OM reveals that the microstructure of specimens is dendrite structure, and the primary dendrite arm spacing decreases from 480 μm to 390 μm with withdrawal rate increasing from 1.5 mm/min to 6.0 mm/min. Different with the common Ni–based superalloys, the size of the γ' phase in the dendritic core is larger than that in the interdendritic area. As withdrawal rate increases  the size of the γ' phase decreases. The average size of the γ' phase in the dendritic core decreases from 3 μm to 1.3 μm and the average size of the γ' phase in the interdendritic area decreases from 1.6 μm to 0.8 μm with withdrawal rate increasing. Meanwhile, the shape of γ' phase tends to regular, and more primary eutectic γ' phase precipitates form in the interdendrite region. The volume fractions of primary eutectic γ' phase precipitates are 0.07\%, 0.18\%, 0.36\% and 0.77\%, respectively at the withdrawal rates 1.5, 3.0, 4.5 and 6.0 mm/min. It has been found that the stress rupture properties are affected by primary dendrite arm spacing and size of γ' phase significantly, i.e., the rupture lives of as-cast specimens increase with increasing withdrawal rate, which may be attributed to the refining microstructure. The above results can be used to optimize the process design for both single crystal specimen preparation and component fabrication of the present alloy IC6SX and may be used as a reference for other Ni--based single crystal alloys.

The tungsten–alloyed 10%Cr (mass fraction) steel, one of the advanced 9%—12%Cr steels, has been widely considered as a preferred candidate for making key components in ultra–supercritical (USC) steam turbines. Due to large amounts of ferrite former in the steel, the formation temperature of δ–ferrite is lowered down, and therefore δ–ferrite is apt to be produced during hot working. However, understanding of the formation mechanism of δ–ferrite and its influence on the mechanic properties of ultra–supercritical steels is still either ambiguous or conflicting. To clarify this problem, in this paper, the microstructure and morphology of δ–ferrite were investigated by optical microscope, scanning electron microscope and energy dispersive spectrum (EDS) analysis. Also, the mechanical properties including the tensile strength, ductility and impact toughness of the studied steel with various volume fraction of δ–ferrite were tested at room temperature. Experimental results indicate that the transformation mechanism of δ–ferrite is closely dependent on the austenitizing temperature. Extremely small amounts of acicular δ–ferrite preferentially nucleate and grow inside the prior austenite grains, if the austenitizing temperature is just a little higher than the equilibrium transformation point of δ–ferrite. While, as the austenitizing temperature increases further, some polygonal δ–ferrites subsequently form on prior grain boundaries and grow quickly. Meanwhile, the repartitioning of solute elements occurrs between δ–ferrite and prior austenite. Both acicular and polygonal δ–ferrites will damage the impact toughness of the studied steel. And in spite of its few amounts, the detrimental effect of acicular δ–ferrite on the mechanical properties, especially the impact toughness, is more severe than that of polygonal δ–ferrite. Additionally, the tensile strength and the area reduction of the studied steel decrease as the amount of δ–ferrite increases, while the elongation hardly changes with the amount of δ–ferrite increasing. As a conclusion, accurately controlling the austenitizing temperature to prevent from the formation of any δ–ferrite is not only necessary but also very important in obtaining perfect overall mechanical properties.

Previous researches indicated that granular bainite (GB) and granular structure (GS) mainly differ in the shape and distribution of islands and the ferrite matrix: firstly, the GB islands distribute regularly and longitudinally in stripe shape, whereas the GS islands distribute disorderedly with irregular morphology; secondly, the matrix of the former is bainitic ferrite, however that of the latter is proeutectoid ferrite matrix. In addition, the properties of GB and GS differ significantly. Under specific conditions the strength and toughness of GB are superior to those of GS whose toughness is poor hence GS should be avoided in steels. It’s important for phase transformation theory study to understand the morphology of GS and its corresponding transformation condition completely; furthermore, its properties can be improved by microstructure optimization. The granular structures of low carbon Mn–Si steels, especially the distribution of GS islands were studied. It was found that the microstructure of steels without Cr after air–cooling is GS consisting of proeutectoid ferrite and islands which distribute in the two forms: irregular and directional respectively. Their forming mechanisms, including forming process of islands and type of proeutectoid ferrite were discussed. Results show that the morphology and distribution of the islands reflect the morphology of proeutectoid ferrite, and the strip islands formation may be controlled by the ledgewise growth of proeutectoid ferrite. There are three formation types for the strip GS islands: (1) long islands formed among Widmannstatten ferritic plates; (2) short and paralleled islands formed in massive proeutectoid ferrites which are formed by ledgewise mechanism; (3) broad and paralleled islands formed in massive ferrites growing along certain low–energy crystal faces. The GS islands may distribute directionally under specific conditions, and not all microstructures of ferrite matrix and paralleled islands are GB. In existence of proper content Cr no granular structure appears in the studied low carbon Mn–Si steel after continuous cooling.

The TWIP (twinning induced plasticity) steel is a new developed super toughness steel. In the TWIP steel, deformation twinning is the dominate mechanism controlled by stacking fault energy (SFE) in austenitic phase during plastic deformation. Since SFE depends on temperature, it has a major influence on mechanical properties of alloys. The evolution of deformation mode in Fe–Mn–C austenitic steels with temperature and SFE has been extensively reported in literatures. However, in Fe–Mn–Al–Si austenitic steels, the literatures only focused attention on the deformation structure and mechanical properties of Fe–28Mn–1Al–0.5Si and Fe–24Mn–3.5Al–0.4Si steels in compression under different temperatures. The relationship between deformation structure and temperature for Fe–Mn–Al–Si TWIP steel under tensile test has not yet been established. More importantly, a thorough investigation on dependence of deformation mechanism on deformation temperature and SFE is stilllacking, which is one of the key factors in alloy design and new processing exploitation. In this paper, the mechanical properties of Fe–25Mn–3Si–3Al TWIP steel and the microstructure evolution with temperature have been investigated through tensile testing at 298, 373, 473 and 673 K. It was found that the strength and elongation decrease with deformation temperatures increasing. The SFE of the TWIP steel, Γ, at different temperatures have been calculated. It was pointed out that when 21 mJ/m²≤ Γ ≤34 mJ/m² in 298 K≤ T ≤373 K, the deformation twinning is a main deformation mechanism, while the slipping is a predominant deformation mode when Γ ≥76 mJ/m2 in T ≥673 K. The SFE value was found to decrease with temperature decreasing, and lower values of SFE would promote deformation twin production and inhibit slip. Deformation twins formed in plastic deformation act as obstacles to dislocations, resulting in high strain hardening effect so that both high elongation and ultimate tensile strength can be obtained at relatively low temperatures.

The mechanical properties and microstructures of Al–5.2Cu–0.4Mg–1.02Ag alloy during different aging processes were studied. The nucleation and coarsening of the main precipitation Ω phase were investigated, and the concentration ledge coarsening mechanism was proposed. The results show that the main precipitated phases are Ω phase and θ‘ phase A large number of fine Ω phase precipitates but a small amount of θ’ phase precipitates are found in the underaged alloy At peak–aging, the volume fraction of both Ω phase and θ‘ phase increases significantly and Ω phase issemi–coherent with the matrix. The equilibrium θ phase is found in subsequent overaging. During this time, Ω phase grows slowly but θ’ phase quickly both in length and thickness. Each of Mg/Ag co–clusters is used as a nucleation site of Ω phase in initial aging stage. The driving force for Ω phase coarsening comes from ledge migration caused by the atomic concentration difference of Mg, Ag and Cu. Since the segregation of Ag and Mg atoms in the interface between Ω phase and matrix reduces the misfit energy of lattice, the velocity of Cu atom moving to Ω phase is limited and Ω phase can keep its platelet shape well and the cohesion destabilization does not occur in long term aging.

Magnesium alloys have emerged as potentially good candidates for numerous applications, especially in automotive industry. Although the commonly used magnesium alloys, such as AZ91 and AM60 based on Mg–Al system have excellent castability, good room temperature mechanical properties and low cost, the application of these alloys has been limited to temperatures below 120℃ because of their poor heat resistance, especially creep property at elevated temperatures. Recent development reported that magnesium alloys with high zinc and low aluminum concentrations (Mg–Zn–Al based alloys) exhibit better creep properties than Mg–Al based alloys at temperatures above 150 ℃ and small amounts of alkaline–earth element (Sr and Ca) additions to the Mg–Zn–Al ternary alloys lead to further improvement of their mechanical properties. The purpose of the present paper is to describe the effects of calcium and strontium additions on the microstructure and mechanical properties of Mg–12Zn–4Al–0.3Mn based alloy. The results indicate that the as–cast microstructure of Mg–12Zn–4Al–0.3Mn alloy consists of the α–Mg matrix and a quasicrystalline Q phase at grain boundaries. Small amounts of Sr addition to the master alloy result in the transition of metastable Q phase to the equilibrium Mg₃₂(Al, Zn)₄₉ phase and the formation of binary eutectic phase Mg₅₁Zn₂₀. Another lamellar eutectic phase Al₂Mg₅Zn₂ is observed in the as–cast microstructure when Ca combined with Sr is added to the base alloy, and its volume fraction increases with increase of Ca addition. The single addition of Sr causes the increase of tensile strength, but decrease of creep resistance at elevated temperatures. However, the creep properties are significantly improved if Sr is added in combination with Ca to the master alloy due to the formation of ternary eutectic phase Al₂Mg₅Zn₂, which shows the high thermal stability at elevated temperatures. The alloy with composition of Mg–12Zn–4Al–0.2Sr–0.4Ca–0.3Mn exibits good creep resistance at 175℃and 70 MPa.

The mechanical properties of Ni–based superalloy are mainly determined by quantity, shape, size and distribution of γ' precipitates. For a given alloy, the quantity, shape, size and distribution of γ' precipitates are mostly affected by solidification parameters during solidification process. In present, the influence of solidification parameters on γ' precipitates has been extensively reported. But unfortunately, these researches on γ' precipitates under as cast condition are mostly intuitive descriptionof solidification phenomena and the in–depth research on the influence of solidification parameters on the morphology, distribution and size of γ' precipitates is little, especially under high thermal gradient directional solidification. In this paper, the influence of cooling rates on the morphology, size and distribution of γ' precipitates in dendrite core and interdendritic areas of directionally solidified nickel–based superalloy DZ4125 was investigated under high thermal gradient about 500 K/cm. The cooling rates used in this experiment were 2.525, 5.15, 13.17, 25.875 and 36.4 K/s, respectively. The relative mechanisms of changes in the morphology, distribution and size of γ' precipitates were discussed. These results show that, with cooling rate increasing, the dendrite microstructure of DZ4125 alloy becomes fine. At the solidification rate of 36.4 K/s, the dendrite morphology changes to a superfine dendrite solidification mode. In this process, the morphology of γ' precipitates changes from cubic to spheric shape and the sphericized speed of γ' precipitates in dendrite core quicker than in interdendritic. Furthermore, the average size of γ' precipitates decreases gradually so that they become well–distributed in both dendrite core and interdendritic. This average size of γ' precipitates in dendrite core is smaller than in interdendritic, however the difference in size decreases with cooling rate increasing. These changes in the morphology, distribution and size of γ' precipitates result mainly from the degree of supersaturation of solute in γ solid solution ΔX, degree of undercooling in γ solid solution ΔT, critical precipitation nucleation work of γ' precipitate ΔG* and solution diffusion coefficient in γ solid solution
D caused by altering cooling rate.

In order to deeply understand the high temperature deformation behaviors of Cu–0.23%Al₂O₃ (volume fraction) alloy, the changes of flow stress and microstructure for this alloy after deformation at high temperatures were investigated by using the Gleeble–1500 hot simulator, metallographic microscope and transmission electron microscope. The results show that the flow stress will change significantly with the thermal compression conditions and is mainly divided into three different stages. In addition, the average activation energy and other material parameters of this alloy deformed at high temperatures were obtained, based on them, the constitutive equation of the peak value yield stress–strain rate–temperature was also established. With increasing of compression temperature, the size and number of dynamic recrystallization grains are increased. However in the case of isothermal compression, with increasing of strain rates, the evolution of metallographical microstructures becomes disequilibrium, the size of subgrain is gradually decreased to about 0.5—1 μm, and the dislocation density is increased at first, and then decreased.

Low costly ferritic stainless steels, especially the Cr₂O₃–forming alloys, are promising interconnect materials for solid oxide fuel cells (SOFCs) due to their thermal expansion compatibility with other cell components. However, the oxidation resistance of commercial ferritic stainless steels in the operating temperature range of 600—800 ℃ is not adequate, forming relatively thick, poorly conducting oxide scale on the surface of the stainless steel interconnect and decreasing the cell performance. Surface modification is necessary to improve the oxidation behavior and electrical property. The present study investigates the effect of a LaCoO₃ protective coating by the sol–gel process on the intermediate temperature oxidation behavior of SUS 430 alloy, which is frequently considered as the interconnect material for SOFCs. X–ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the phase structure, surface morphology and composition of the coating and the oxide scale. The "4–probe" method was employed to determine the area specific resistance (ASR) of the surface oxides. Long–term thermally cyclic oxidation at 750 ℃in air has shown that the oxidation kinetics obeys the parabolic rule with a rate constant of K=4.18×10−15 g²/(cm⁴·s), which is 1—2 orders of magnitude lower than that of the uncoated alloy, the LaCoO₃ protective coating effectively suppresses the formation of Cr₂O₃ and slows down the growth of MnCr₂O₄ spinel. As a result, the oxidation resistance and electrical conductivity of the coated SUS 430 alloy are significantly enhanced, resulting in an ASR at 750 ℃of only 3.13 m·cm² after oxidation at 750 ℃ for 850 h in air and an extrapolated ASR of 21.5 m·cm² for 4×10⁴ h oxidation.

Diamond–like carbon (DLC), which used to describe a wide range of amorphous carbon films containing sp³ bond, has been extensively studied and applied in the fields of mechanics, electronics, optics and medicine, due to their excellent properties, such as high hardness and wear resistance, low friction coefficient, high chemical inertness, low expansion coefficient, well biocompatibility, and so on. However, high internal stress and low thermal stability are the main problems in applications of DLC. On the one hand, high internal stress is generated in the growth process of DLC, which greatly reduces the adhesion strength of the film to substrate, making the film easily delaminate from the substrate. On the other hand, the DLC will graphitize and be obviously oxidized when the temperature is over 350 ℃, leading to the deterioration of properties evidently. Non–metal N has strong affinity with transition metal Cr and their compound CrN has high hardness and oxidation resistance. So it is expected that composite film with hard CrN crystalline phase imbedded within DLC amorphous matrix maybe obtained by doping N and Cr simultaneously. In this paper, the uniform, smooth and dense C–N–Cr films with different compositions were deposited on cemented carbide substrate at different nitrogen flow rates by pulsed bias arc ion plating. The surface morphology, composition, structure and properties of C–N–Cr films were investigated by SEM, GIXRD, XPS, Raman spectra and Nano–indentation, respectively. The results show that the nitrogen content in the C–N–Cr films increases linearly and then slowly with nitrogen flow rate increasing, while the Cr content first keeps stable and then decreases linearly. The C–N–Cr films have high hardness (>30 GPa) and elastic modulus (>500 GPa) when the nitrogen flow rate is not more than 20 mL/min, above which the hardness and elastic modulus decrease drastically and only have the value of 13.6 and 190.8 GPa when the nitrogen flow rate is 100 mL/min.

FeCuCrVSiB soft magnetic films have been prepared using radio frequency sputtering without or with a constant magnetic field of about 72 kA/m along the longitudinal direction of film plane, and then their soft magnetic properties and giant magnetoimpedance (GMI) effects were measured. The results obtained show that the magnetic field applied during the deposition process improves significantly the soft magnetic properties of the sample. For example, its coercive force decreases from 1.080 kA/m of the non–field–deposited state to around 0.064 kA/m and its effective permeability ratio increases from 10% to 106%. The GMI effect is closely connected with this permeability ratio. The GMI effect can not almost be detected in non–field–deposited samples, while it becomes evident for field–deposited samples. The maximum values of longitudinal and transverse GMI ratios are 22% and 20% at the frequency of 13 MHz, respectively. The GMI effect in the field–deposited sample is much better than in annealed FeCuNbSiB film with the same thickness.

As a new kind of engineering material, the metallic glass can be used widely due to its excellent properties such as high strength, hardness and elastic energy and low corrosion resistance. The size of metallic glasses is generally small, which is the main limitation for their application. How to prepare a larger size metallic glass becomes one of main targets in metallic glasses research. To prepare larger size metallic glasses, one method is to optimize their chemical compositions, and another is to join small size metallic glasses together by welding. In this paper, the Zr₅₅Al₁₀Ni₅Cu₃₀ bulk metallic glass (BMG) has been successfully jointed by friction welding under the conditions of rotational speed from 4×10³ to 5×10³ r/min, friction pressure from 80 to 100 MPa, friction time from 0.2 to 0.4 s, upsetting pressure 200 MPa and upsetting time 2 s. The welded joint has been examined using SEM, XRD and TEM, and it is proved that the welded zone still keeps an amorphous structure. The plasticity of this metallic glass has strong temperature sensitivity near the glass transition temperature T_g. Above T_g, the metallic glass possesses a good plasticity which is necessary for friction welding of metallic glasses.

As a Ni3Al precipitation strengthening alloy, Ni–Cr–Al alloy is one of typical structural materials applied in high temperatures. Much work has been done concerning its structure transformation from fcc to L1₂ during the process of ordering and phase separation. However, the study so far we know on the phase transformation in very early precipitation stage, especially on the phase transformation of unstable pre–precipitation phase, was not yet sufficient. Microscopic phase–filed method is used for describing the temporal and spatial evolution of atomic site in lattice. This method is employed to study the pre–precipitation during the structure transformation from fcc to L1₂ in Ni₈₀Al₁₃Cr₇ alloy in this paper. The relationship between the occupation probability changes in Al and Cr atoms on (100) and (200) planes respectively and structure evolution of Ni₃(Al, Cr) will be inveatigated. The simulation results demonstrate that at in very early aging stage, the composition order parameters of Al and Cr atoms keep unchange on both (100) and (200) planes. However their long range order parameters are equal in these two planes and gradually increase with aging time until
the first in situ transformation by congruent ordering at that time the L1₀ pre–precipitation phase with low long range order is formed. By prolonging aging time, their long range order parameters continue increase once they attain to the respective certain values, the composition order parameters and the long range order parameters of Al and Cr atoms on (100) plane become increasing rapidly but those on (200) plane decreasing quickly, The second in situ transformation occurs and the L1₀ is gradually
transformed into L1₂.

The microscopic phase–field model based on long range order (LRO) method was proposed to study Cr substitution behavior in Ni₇₅Al₁₅Cr₁₀ alloy aged at 1073 K. This has been demonstrated by short range order (SRO) methods and experiments such as pseudo–potential, Monte Carlo method and Rutherford back scattering analysis (RBS). Adding ±4 meV to the ordering energy of Ni–Al, Ni–Cr and Al–Cr in 1st—4th nearest–neighborhoods is used to describe the influence of potential field on substitution. On the analysis of atomic images, the order parameters and Cr occupation probabilities, results show that there are coexisted Ni–Al anti–site and Cr substitution for Ni and Al in L12 ordered phase, and Cr substitution occurs much more often than Ni–Al anti–site. As the ordering energies of Ni–Al and Ni–Cr in 1st and 3rd nearest–neighborhoods increase, there is a more increasing tendency of substitution of Cr for Al than for Ni. For the 2nd and 4th nearest–neighborhoods, the
ordering energy makes the tendency of substitution of Cr for Ni increase. Otherwise, with the 1st and 3rd nearest–neighborhoods ordering energies of Al–Cr increasing, the tendency of substitution of Cr increases for Ni but decreases for Al, which is opposite to the cases for the 2nd and 4th nearest–neighborhoods.